This invention relates to the use of an organocobalt (III) catalyst to polymerize vinyl chloride monomer. In particular, it relates to the use of an acid activated cationic catalyst having two organic ligands covalently bonded to a cobalt atom and four ligands donating electron pairs to the cobalt atom, where the various ligands can be bridged together.
Commercially, a peroxide initiator is used to produce poly(vinylchloride) (PVC) from vinyl chloride monomer (VCM). Peroxide initiators are difficult to handle because they are unstable and can explode if proper safety precautions are not followed. Since the reaction mixture containing the peroxide initiators must be heated to start the polymerization process, the production of PVC periodically grinds to a halt while reactors are heated to the necessary temperature. In addition, when a peroxide is used it is incorporated, which can destabilize the polymer.
Cationic organocobalt (III) catalysts have been used to polymerize various monomers, including methyl methacrylate (Gridnev A. A., et al.--Dokl. Akad.Nauk SSSR, v.267, N.1, p. 103 (1982)), 1,1,2-trifluoro-1,3-butadiene (Rogova E. V., et al.--Polymer Science, Ser.B, v.37, N.9-10, p.447 (1995)), and styrene Russian Patent SU 1816764 (1993)). However, catalysts used in the addition polymerization of unsaturated monomers tend to be specific to a given monomer. For example, many metallocene catalysts that will readily polymerize ethylene or styrene will not polymerize vinyl chloride.